that is one indicator that your pilot volume is about 100 times bigger than maximum

what you mean ??can you explain ?

The blowgun is the pilot on that 10ft sprinkler valved cannon. The red tube is the pilot line. Now that pilot line holds a large amount of air that the relatively small (and low-ish flow) blowgun has to exhaust. Now because theres sooo much pilot volume, it's not going to exhaust as fast as it would if the pilot volume was smaller. The speed at which the pilot volume can be vented decides how fast the diaphragm in the sprinkler valve will open. The faster you vent the pilot, the faster the valve will open. So, logic dictates that the slower you exhaust the pilot volume then the slower the valve will open. This causes a stuttered flow through the sprinkler valve and this is what you see in the video.

If he were to cut that red tube dow then he would see that the sprinkler valve would open faster and therefore there would be more power.